1. Field of the Invention
The present invention relates to patient interface devices, and, in particular, to a patient interface device having an adjustable, integrated headgear and frame for allowing the fit of the patient interface device to be selectively adjusted.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure.
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including a cushion component on the face of a patient. The cushion component may be, without limitation, a nasal mask that covers the patient's nose, a nasal cushion having nasal prongs that are received within the patient's nares, a nasal/oral mask that covers the nose and mouth, or full face mask that covers the patient's face. The patient interface device interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head. Because such patient interface devices are typically worn for an extended period of time, it is important for the headgear to maintain the cushion component of the device in a tight enough seal against the patient's face without discomfort.
For patient interface devices, a key engineering challenge is to balance patient comfort against stability of the device as well as minimize unintentional gas leakage at the patient-cushion interface. As a patient changes sleeping positions through the course of the night, the mask portions of patient interface devices may become dislodged, and the seal against the patient's may be broken. A dislodged mask portion can be stabilized by the increasing strapping force provided by the headgear, but increased strapping force tends to reduce patient comfort. This design conflict is further complicated by the widely varying facial geometries that a given patient interface device design needs to accommodate. Such wide variation in facial geometry is demonstrated in Table 1 below (source: PeopleSize2008 database, OpenErgonomics Ltd.).
TABLE 15% US population95% US populationVariationMin (mm)Max (mm)(mm)Nose Tip Depth15238Nose Length445713Eye corner to15118433back of headNose base to18221634back of headCheekbone width12615024Head Breadth14016727
To further complicate this issue, individual tolerances for comfort also vary widely. For instance, given the same level of mechanical pressure on a specific area of the face, one person may develop significant marks, blisters, or open sores, while another person may feel no effects at all.
One known patient interface device is the Swift LT available from ResMed Inc. In that device, a plastic stiffener is fixedly stitched to the fabric headgear extensions. This allows for stability of the mask, but does not allow for relative motion between the fabric and the stiffener. Therefore, a patient cannot properly adjust this to their specific needs.
Another known patient interface device is the ComfortGel nasal mask available from Philips Respironics. That device includes four attachment points between the fabric headgear and the plastic mask that allow for relative motion between the fabric headgear and the plastic mask. However, in this device, the mask is free to move in many degrees of freedom, which can lead to instability (especially for a pillows style masks).